Magnetic fields are vector fields which emanate from magnetic dipoles and moving electrical charges. The detection of weak magnetic fields with high spatial resolution is an important problem in diverse areas such as fundamental physics, materials science, geotechnical exploration, navigation, data storage and biomedical science. A magnetometer is an instrument which is used to measure the strength and/or direction of a magnetic field. It is desirable that a magnetometer be comparatively inexpensive, suitable for operation in a wide range of environments, and provide high sensitivity and spatial resolution.